Gastric cancer is the second most common malignancy worldwide. Based on histology, gastric cancer can be classified as either diffuse or intestinal-type. A continuum of progression from chronic superficial gastritis through atrophic gastritis, intestinal metaplasia, ultimately leading to dysplasia, has been proposed for the intestinal type of gastric cancer, which accounts for 70% of gastric cancer cases. Several large prospective cohort studies, have suggested a positive association between tooth loss and the risk of gastric cancer. However, the underlying mechanisms are not known and the interpretation of tooth loss is not clear. Periodontal disease is the most frequent cause of tooth loss for people over 40 years of age. However, no studies have evaluated the association of periodontal disease and gastric cancer or precancerous lesions. We propose to conduct a hospital-based case-control study to test the hypothesis that periodontal disease is associated with an increased risk of chronic atrophic gastritis and intestinal metaplasia, the well-established gastric precancerous lesions. Among individuals undergoing upper endoscopy at Veterans Affairs New York Harbor Healthcare System (VANYHHS) and Bellevue Hospital Center, a total of 110 controls with either no gastric lesions or chronic superficial gastritis only, and 110 cases of chronic atrophic gastritis and/or intestinal metaplasia, will be invited to have a comprehensive oral examination. We will also measure major pathogens of destructive periodontal disease that are related to systemic inflammation and potential pathogens relevant to oral nitrate-reduction. We aim to gain knowledge on the role of oral health in the development of gastric precancerous lesions and in gastric cancer etiology. This project has the potential to address an important public health topic relevant to oral health, expanding the scope of the National Institute of Dental and Craniofacial Research (NIDCR)'s clinical research, and identifying a population that may require special needs of oral health. PUBLIC HEALTH RELEVANCE: This project aims to evaluate the associations of clinical indices and major pathogens of periodontal disease with gastric precancerous lesions. Findings of the study may help identify a population that is at a high risk of gastric cancer.